Electromagnetically-operated device



H. R. CANFIELD.

ELECTROMAGNETICALLY OPERATED DEVICE.

APPLICATION FILED JAN. 19, 1.917 RENEWED MAY 17.1920.

1,354,881. Patented 001:. 5,1920.

2 SHEET$-SHEET I.

i 3 as INVENTOR.

H. R. CANFIELD.

ELECTBCBMAGNETICALLY OPERATED DEVICE. APPHCATION ELLED JAN. I9, 1917. RENEWED MAY 17.1920.

1,354,881, Patented Oct. 5, 1920.

2 SHEETSSHEET 2.

Hear/y Canfi/a BY A TTORNEY.

UNITED-STATES PATENT OFFICE.

HARRY IR. CANFIELD, CLEVELAND, OHIO, ASSIGNOR TO THE ELECTRIC CON- TROLLER & MANUFACTURING COMPANY, OF CLEVELAND, OHIO, A CORPORA- TION OF OHIO.

ELECTROMAGNETICALLY-OPERATED DEVICE.

Specification of Letters Patent.

Patented Oct. 5, 1920.

Application filed January 19, 1917, Serial No. 143,281. RenewedMay 17, 1920. Serial No. 382,082.

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Be it known that I, HARRY R. CANFIELI), a citizen of the United States, residing at Cleveland, in the county of Cnyahoga and State of Ohio. have invented new and useful Improvements in Electromagnetically-Operated Devices, of which the following is a specification.

My invention relates to magnetically operated devices, and particularly to magnetically operated switches.

It is one of the objects of this invention to provide an electromagnetic switch which, when its operating winding is energized above a predetermined value, ren'iains in its normal, or open, position without restraint due to magnetism produced by the winding and which closes when the energization thereof falls to a predetermined value. In my application, Serial Number 583,000, filed September 21. 1910, I show a switch which is magnetically held in its open position when the current in its operating winding is relatively high and magnetically closed by the flux of its operating winding when the current is reduced to a predetermined value, but in the present invention the operating winding produces no magnetic force preventing the switch from closing. The switch has, when its winding is unenergized, a normal bias to the open position and remains open without assistance from the winding when the current is above a predetermined value.

In the accompanying drawings, Figure 1 shows a side view partly in section and partly broken away of one form of my invention; Fig. 2 is a front elevation of a part of the form shown in Fig. 1; Figs. 3, 4, 5, 6, and 7 are views similar to Fig. 1 with some of the parts omitted, showing others of the many forms in which my invention may be embodied.

Referring to Fig. 1 of the drawings, the energizing winding is shown at 1. The magnetic circuit energized by the winding 1 has the frame 2, the pole-piece 3, the armature 4, and the plunger 5. The pole-piece 3 may fit loosely in the frame and is supported thereupon by the shoulder 6. The plunger 5 which is a hollow cylinder closed at the lower end is normally suspended in position by a stem 7, rigidly connected thereto by the threads 8 and the lock-nut 9, the stem passing loosely through the pole-piece 3 and having a head 10 resting thereupon. The armature 4 has the tail-piece 11, preferably restricted in cross-sectional area, and is mounted loosely on the stem 7, being free to move axially thereon. The tail-piece 11 carries a non-magnetic sleeve 18 by which it is spaced radially from the plunger 5 to prevent its sticking thereto magnetically. The armature 4 also has a collar 12, by which the armature and tail-piece are supported in position on the. end of the non-magnetic sleeve 13. The sleeve 13, preferably made of nonmagnetic material of low electrical resistance, is threaded into the frame 2 at 14, and may thereby be adjusted axially in the frame and fixed at any adjustment by the lock-nut 15.

By thi construction, two working air gaps are provided, the gap 16 between the pole-piece 3 and the armature 4, and the gap 17 between the armature 4 and the plunger 5. These air gaps may be adjusted simultaneously by adjusting the axial position of the sleeve 18 or may be adjusted independently by adjusting the position of the sleeve 13 and also the position of the plunger 5 on the stem 7 by means of the threads 8.

Under the magnetic influence of the winding, in a manner to be described later, the magnetic flux in the air gaps 16 and 17 will cause the plunger 5, or the plunger 5 and the armature 4, to be lifted, closing the air gap 17 or the air gaps 16 and 17. When the plunger 5 is lifted, it carries with it the stem 7 and the head 10. The movable contact member 20 mounted on the head 10 will thereby be lifted and will make contact with the brushes or stationary contacts 21 (see Fig. 2). Each of the brushes 21 is provided with a stud 22 to which electrical connections may be made, and the engagement of the contacts 20 and 21 may thus be used to close an electric circuit.

The operation of my invention is as follows: When the winding 1 is energized with current below a predetermined value, the magnetic flux will flow in a divided ath, part flowing through the tail-piece 11 and the armature 4, and part flowing in the plunger 5, the gap 17, and the armature 4; the restricted section of the tail-piece 11 will cause the greater part of the flux to flow in the latter path, and the plunger 5 will be lifted into enga e ent with the armature 4 closing the ga This movement communicated througi the stem 7, lifts the contact plate 20 and closes the switch. The reluctance in the magnetic circuit is thereby decreased, increasing the magnetic flux in the gap 16 and this gap closes, lifting the plunger 5 and the armature 4, carrying the stem 7 and the contact plate 20 still higher, securely sealing the switch contacts. If desired, the brushes 21 may be so spaced from the contact plate 20 that the switch will not be closed by the closure of the gap 17 only, but by the closure of both gaps 16 and 17. If, however, the winding 1 be initially energized with current above a predetermined amount, the flux in the magnetic circuit while building up to full strength changes very rapidly inducing in the sleeve 13 a counter magnetomotive force and temporarily choking the flux out of the gap 17. Flux flows, however, in the gap 16 and lifts the armature 4, closing the gap 16 and increasing the gap 17 but the plunger 5 Will not be lifted because of insufiicient flux and pull in the gap 17. When, however, the flux in the magnetic circuit is built up to full strength, the greater part thereof flows through the tailpiece 11 and the armature 4 and very little, if any, flows in the gap 17 The armature 4 will thus be still held up and the magnetic pull in the increased gap 17 will still be insufficient to lift the plunger 5, and the switch will remain open.

Upon a reduction of current in the winding to a point sufiiciently below the predeter-- mined value, the armature 4 is released and moves to its original position, thereby reducing the gap 17, and causing the switch to close, as has been described. After the switch has closed, it remains closed until the current in the winding has been reduced to a very low value or approximately to zero whereupon the parts resume their normal positions. In order to facilitate the prompt release of the armature4 when the current is reduced, a non-magnetic spacer 23 of suitable thickness may be employed on the end of the armature 4, as shown, or on the end of the pole-piece 3, as will be understood. It is obvious that the said predetermined value may be changed at will by means of the adjustments above described which vary the sizes of the gaps 16 and 17 It will be apparent from the above description that the higher the electrical resistance of the sleeve 13, the higher will be the predetermined current necessary (at a given adjustment) to choke the flux out of the gap 17 and lift the armature 4 without lifting the plunger 5, and the greater will be the subsequent amount of current reduction necessary to release the armature 4 and cause the switch to close. In following out this principle, I have found that without any sleeve 13 there is still a predetermined value for the device and, therefore, the sleeve 13 may be omitted, except in cases where a comparatively small reduction of current to cause the switch to close is required.

The form of my invention as shown in Fig. 3 is practically the same as that shown in Fig. 1, except that instead of the plunger 5 being a hollow cylinder surrounding the tail-piece 11, the tail-piece 11 is made in the form of a hollow cylinder surrounding the plunger 5", and the non-magnetic sleeve 13 is placed between the plunger 5 and the tail-piece 11 thus obviating the ne cessity of the sleeve 18. In this form, when the winding 1 is energized with current above the predetermined value, the flux has a direct path into the armature 4 and the gap 16, free from choking action of the sleeve 13 requiring a lower predetermined value of current to lift the armature 4 without lifting the plunger 5.

In the form shown in Fig. 4, the tailpiece is omitted from the armature 4. and the lower end of the armature 4 rests on the non-magnetic sleeve 13. A magnetic path consisting of the branches 24 projecting inwardly from the main frame 2 and having choking rings 25 is provided as a shunt for the gap 17. When the armature 4 is in its normal position and the winding is energized with current below the predetermined value, the flux flows from the plunger 5 across the gap 17 into the armature 4, lifting the plunger 5 and closing the switch as heretofore described. Little or no flux flows from the plunger 5 into the branches 24, the reluctance of the gap 26 between the plunger 5 and the branches 24 being greater than that of the gap 17. lVhen the winding is energized with current above the predetermined value and while the flux is building up to full strength, the non-magnetic sleeve 13 chokes the flux out of the gap 17 and the choking rings 25 choke the flux out of the branches 24 and the flux flowing in the armature 4 and the gap 16 lifts the armature 4, closing the gap 16 and increasing the gap 17. \Vhen, however. the flux in the magnetic circuit is built up to full strength, a small part thereof flows through the gap 17 and the armature 4, holding the armature 4 in its upper position and the greater part of the flux flows from the plunger 5 through the gap 26 and the branch members 24. The magnetic pull in the increased gap 17 will be insufficient to lift the plunger 5 and the switch will remain open. Upon a reduction of current in the winding, the armature 4 is released and moved to its original position, thereby rebeen described. The branches 24 besides serving the purpose just described have a two-fold effect: First, when the winding is energized with current above the predetermined value and the armature 4 has been lifted, without the branches 24, an excess of current or an overload, if permitted to flow in the winding, mi ht produce sufiicient flux in the gap 17 to li t the plunger 5 and close the switch but with the branches 24 sufiicient flux from such excess current would be shunted from the gap 17 by the branches 24 to prevent the lifting of the plunger; and second, when the windlng is energized with current above the predetermined value, and after the armature 4 has been lifted and the flux in the circuit has reached full strength and the choking action of the rings 25 has ceased, some of the flux which flowed through the gap 16 to lift the armature flows into the branches 24 so that a small reduction of current from the predetermined value will cause the armature 4 to be released, thus giving a small change of value between the current at which the switch will remain open and that at which it will close. In some cases, this small change of value is desirable.

The form of my invention shown in Fig. 5 is practically the same as that in Fig. 4, except that the branch magnetic circuits 24 are omitted. In the forms shown in Figs. 4 and 5, the armature 4 is approximately cylindrical, and the cross-sectional areas of the pole-piece 3, the armature 4, and the plunger 5 are approximately equal. The form shown in Fig. 6 is practically the same as that shown in Fig. 5 except that in Fig. 5 the cross-sectional areas of the pole-piece 3 and the upper end of the armature 4 are approximately equal, and larger than the cross-sectional areas of the plunger 5 and the lower end of the armature 4, which are also approximately equal; and the armature in Fig. 6 has a reduced lower end within the sleeve 13. The form shown in Fig. 7 is practically the. same as that shown in Figs. 5 and 6, except that the cross-sectional areas of the pole-piece 3 and the upper end of the armature 4 are approximately equal and smaller than the cross-sectional areas ot-the plunger 5 and the lower end of the armature 4, which are also approximately equal.

In Fig. 7 I have shown another means alternative to that shown in Fig. 4 for preventing current in excess of the predetermined value, such as an overload, from closing the switch. I provide a spring 26 and a comparatively large gap 16. Under normal conditions when the winding is energized above the predetermined value, the armature is lifted bringing the upper end of the spring 26 into engagement with the frame at 27, partially closing the gap 16.

If now an overload or excess of current flows in the winding the spring will be compressed and the gap 16 still further closed by the further upward movement of the armature 4, thus still further increasing the gap 17 whereby the flux in the gap 16 due to the overload or excess value of current will be insufficient to close the switch. IVhen the current is reduced toward the switchclosing value, the spring 26 gradually expands so that the value of current at which the armature 4 finally is released and moves to its original position, is uninfluenced by variations which may occur in the tension of the spring.

As is well known, switches having the general operating characteristics described herein may be used for controlling the starting resistance of an electric motor, and it is, therefore, not deemed necessary to show herein an application of my invention to practical uses. It is apparent that the switches herein described may be substituted for the accelerating switches shown in many motor control systems. For example, my switches may be readily substituted for the accelerating switches shown in my said application, Serial Number 583,000, or in Halls Patent No. 1,197,584.

My invention is not limited in its-application to motor-controlling or motor-starting purposes. Many changes and modifications other than those shown may be made without departing from the spirit of my invention; for example, other means of adjustment may be provided to vary the predetermined value of current at or below which the switch will close and above which it will remain open; and the spring 26 or its equivalent may be used with the forms shown in Figs. 1 to 6, or with other forms; and the relative shapes and proportions of the pole-piece 3, the armature 4, and the plunger 5 may be further varied; and the relative axial position of the winding with respect to the magnetic circuit may be varied, the effects which such modifications will have upon the operation of the device being apparent to those skilled in the art.

I claim- 1. A controlling device for electric circuits containing a winding, a movable switch operating member having mechanical bias to the position in which it is when the switch is open and the winding is unenergized, and means whereby the switch-operating member remains in said position irrespective of magnetic action thereon when the current is relatively high and moves to the switchclosing position when the current falls to a predetermined value.

2. A controlling device for electric circuits containing a winding, a movable switch member having bias to open position when thewinding is unenergized, the switch member remaining in open position by means of said bias onl when the current is relatively high, and means whereby the switch mem er moves to closed position when the current falls to a predetermined value.

3. A controlling device for electric circuits containing a winding, a movable switch-operating member adapted to be heldclosed by the winding and having mechanical bias to the position in which it is when the switch is open and the winding is unenergized, and means whereby the switchoperating member remains in said position irrespective of magnetic action thereon when the current is relatively high and moves to the switch-closing position when the current falls to a predetermined value.

4;. In an electromagnetic switch, a winding, a movable switch-operating member having a bias to the position it has when the switch is open and the winding is unenergized, a second movable member, and means whereby when the current in the winding is relatively high, the second movable member is operated to prevent the switch-operating member from moving, and, when the current falls to a predetermined value, the switchoperating member is actuated.

5. In an electromagnetic switch, a winding, a movable switch-operating member having a bias to the position it has when the switch is open and the winding is unenergized, a second movable member separated from the switch-operating member by a gap for operating the latter member, and means whereby, when the current in the winding is relativelv high, the second member is actuated to increase the said gap to prevent the operation of the switch-operating member.

6. In an electromagnetic switch, a winding, a movable switch-operating member having a bias to the position it has when the switch is open and the winding is unenergized, a second movable member, and means including a magnetic circuit energized by the winding an having an operating gap for the switch-operating member. and means whereby when the current in the winding is relatively high, the second movable member is operated to lengthen the gap.

7. In an. electromagnetic switch, a winding, a movable switch-operating member having a bias to the position it has when the switch is open and the winding is unenergized, a second movable member, and means whereby when the current in the winding 1s relatively high, the second movable member is operated to prevent the switch-operating member from moving, and, when the current falls to a predetermined value, the latter member resumes its said position and causes the operation of the switch-operating member.

8. In an electromagnetic switch, a winding, a movable switch-operating member having a bias to the position it has when the switch is open and the winding is unenergized, a second movable member, a magnetic circuit having the second member movable between the switch-operating member and one pole of the magnetic circuit, and means whereby, when the current in the winding is relatively high, the switch-operating member is prevented from moving whgn the second movable member is actuate Signed at Pittsburgh, Pa., this 17th day of January, 1917.

HARRY R. OANFIELD. 

